DE102019133816A1 - Pressure sensor for determining a relative pressure variable - Google Patents

Abstract

Pressure sensor (1) for determining a relative pressure variable, comprising: - a relative pressure transducer (20) with a first measuring membrane (21) and a first circuit (22) for converting a pressure-dependent deformation of the first measuring membrane (21) into the relative pressure variable, - an absolute pressure transducer ( 70) for determining an absolute pressure variable, - a diaphragm seal (30) with a diaphragm seal body (31a, 31b, 31c) in which there is a pressure chamber (32) filled with a transmission fluid (39) and in which a filling body (33) with two recesses is arranged to fill cavities between the walls of the pressure chamber (32) and the relative pressure transducer (20) and absolute pressure transducer (70) arranged in the recesses; the ambient pressure.

Description

The invention relates to a pressure sensor for determining a relative pressure variable.

Pressure sensors are used to record pressures and are used in industrial measurement technology. Depending on the application, differential pressure sensors or relative pressure sensors are used.

Relative pressure sensors are used to measure a pressure that is to be measured from the outside on a measuring membrane in relation to a reference pressure supplied to the pressure chamber, e.g. atmospheric pressure. They are used in particular in industrial metrology to measure relative pressures.

In pressure measurement technology, so-called semiconductor pressure transducers, e.g. silicon chips with doped resistance elements, are often used as pressure-sensitive elements. Corresponding pressure transducers typically have a measuring membrane, one side of which is exposed to a first pressure and the second side of which is subjected to a second pressure during measuring operation. The acting pressures cause a resulting deflection of the measuring membrane, which corresponds to the relative pressure to be measured. Semiconductor pressure transducers are usually very sensitive and are therefore not directly exposed to a medium whose pressure is to be recorded. Instead, diaphragm seals filled with a transmission fluid are connected upstream.

For this purpose, diaphragm seals regularly have a massive, typically multi-part diaphragm seal body on which at least one separating membrane is arranged on the outside. The separating membrane closes off a first pressure receiving chamber which is connected via a first hydraulic path to a pressure chamber in which the relative pressure transducer is arranged in such a way that the pressure applied to this separating membrane is fed to a first side of the measuring membrane. A second pressure is applied to the second side of the measuring membrane, for example via a capillary. The relative pressure transducer can thus determine the relative pressure variable on the basis of the two pressures supplied.

Diaphragm seals are usually used in automation systems in industrial measurement technology to carry out or control a process, but are also used in other areas, for example in a ship or an airplane. Here the pressure sensors are used to monitor the pressure of, for example, containers for gases and liquids such as oxygen or water, oils, fuel, etc.

In systems of this type, but also in ships and aircraft, there can be unwanted or undesired changes in the room pressure in the vicinity of the installation location of the diaphragm seal, which can endanger the safety of the process and / or the people on site.

It is therefore an object of the invention to propose a pressure sensor which can detect unwanted or undesired changes in room pressure in a simple manner.

The object is achieved according to the invention by the pressure sensor according to claim 1.

• - ein Relativdruckmesswandler mit einer ersten Messmembran und einer ersten Schaltung zum Wandeln einer druckabhängigen Verformung der ersten Messmembran in die Relativdruckgröße,
• - einen Absolutdruckmesswandler zum Ermitteln einer Absolutdruckgröße,
• - einen Druckmittler mit einem Druckmittlerkörper in dem sich eine mit einer Übertragungsflüssigkeit gefüllte Druckkammer befindet, in der ein Füllkörper mit zwei Aussparung angeordnet ist, um Hohlräume zwischen Wänden der Druckkammer und den in den Aussparungen angeordneten Relativdruckmesswandler und Absolutdruckmesswandler auszufüllen, wobei sich ein erster druckkommunizierender Pfad zwischen einer ersten Öffnung und einer zweiten Öffnung durch den Druckmittlerkörper erstreckt, wobei die erste Öffnung mit einer Trennmembrane verschlossen ist, die mit einem ersten Druck eines Mediums beaufschlagbar ist, um den ersten Druck in den ersten Pfad einzuleiten, wobei der erste Pfad mit der Übertragungsflüssigkeit gefüllt ist und an einer der zweiten Öffnungen in der Druckkammer mündet, so dass die durch den Absolutdruckmesswandler ermittelte Absolutdruckgröße den ersten Druck repräsentiert und ferner der Relativdruckmesswandler auf einer ersten Messmembranseite der ersten Messmembran mit dem ersten Druck beaufschlagt ist, wobei eine zweite Messmembranseite der ersten Messmembran über einen zweiten druckkommunizierenden Pfad mit einem Umgebungsdruck beaufschlagt ist, so dass die Verformung der ersten Messmembran die Relativdruckgröße zwischen dem ersten Druck und dem Umgebungsdruck repräsentiert;
• - eine Signalverarbeitungseinheit, die dazu eingerichtet ist, anhand der Absolutdruckgröße und der Relativdruckgröße eine unerwünschte Änderung des Umgebungsdrucks festzustellen.

The pressure sensor according to the invention for determining a relative pressure variable comprises:

• - A relative pressure transducer with a first measuring membrane and a first circuit for converting a pressure-dependent deformation of the first measuring membrane into the relative pressure variable,
• - an absolute pressure transducer for determining an absolute pressure variable,
• - A diaphragm seal with a diaphragm seal body in which there is a pressure chamber filled with a transmission fluid, in which a filling body with two recesses is arranged to fill cavities between the walls of the pressure chamber and the relative pressure transducer and absolute pressure transducer arranged in the recesses, with a first pressure-communicating path between a first opening and a second opening through the pressure transmitter body, the first opening being closed with a separating membrane to which a first pressure of a medium can be applied in order to introduce the first pressure into the first path, the first path containing the transmission fluid is filled and opens at one of the second openings in the pressure chamber, so that the absolute pressure variable determined by the absolute pressure transducer represents the first pressure and furthermore the relative pressure transducer on a first measuring membrane side of the first measuring membrane with de The first pressure is applied, a second measuring membrane side of the first measuring membrane being acted upon by an ambient pressure via a second pressure-communicating path, so that the deformation of the first measuring membrane represents the relative pressure variable between the first pressure and the ambient pressure;
• - a signal processing unit which is set up to determine an undesired change in the ambient pressure on the basis of the absolute pressure variable and the relative pressure variable.

According to the invention, a pressure sensor is proposed which, in addition to the relative pressure transducer, which measures a process pressure in relation to an ambient pressure, also includes an absolute pressure transducer, which measures only the process pressure, all the more so an undesired change in room pressure, for example in the event of a deflagration, a pressure drop in the hold of an aircraft or a To determine or detect flooding of a ship's hold.

The invention is based on the consideration that when the ambient pressure changes, only the relative pressure variable detected by the relative pressure transducer changes, whereas the absolute pressure variable of the process pressure detected by the absolute pressure transducer is constant. Thus, a signal processing unit can use the two pressure variables to determine whether there is an undesired or even dangerous change in the room pressure.

wobei Prel die Relativdruckgröße des Relativdruckmesswandlers, Pabs die Absolutdruckgröße des Absolutdruckmesswandlers und α ein Anpassungs- oder Kalibrierungskoeffizient darstellen.For this purpose, the signal processing unit can be set up, for example, to continuously check whether the following equation is met: $$\text{Prel}=\mathrm{\alpha }\text{Pabs}$$

where Prel is the relative pressure variable of the relative pressure transducer, Pabs the absolute pressure variable of the absolute pressure transducer and α represents an adaptation or calibration coefficient.

wobei Prd ein der Signalverarbeitungseinheit zugänglich gemachter, bspw. abgespeicherter, ortsüblicher Raumdruck ist und L[%] eine Änderung des ortsüblichen Luftdrucks über die Jahreszeiten, Wetterstand, Temperatur usw.. in Prozent, wobei im Normalbetrieb vorzugsweise gilt, dass P2 = Prd.An advantageous embodiment of the pressure sensor according to the invention can provide that the signal processing unit is also set up to detect a change in the ambient pressure ( p2 ) determine if $$\left|\frac{\text{P.}2-\text{Prd}}{\text{Prd}}\right|>n\cdot \mathrm{L.}\left[\%\right],n\in N$$

where Prd is a, for example, stored, customary room pressure made accessible to the signal processing unit and L [%] is a change in the customary local air pressure over the seasons, weather conditions, temperature, etc. in percent, whereby in normal operation it preferably applies that P2 = Prd.

L [%] can, for example, be approx. 0.5% at a customary room pressure of 1013 hPa (approx. 1 bar) and a maximum change of approx. 5h Pa due to the seasons and / or weather conditions.

A further advantageous embodiment of the pressure sensor according to the invention can provide that the absolute pressure transducer has a second measuring membrane to which the first pressure is also supplied on a first membrane side and to which a vacuum is applied on a second membrane side, the absolute pressure transducer also having a second circuit for converting a pressure-dependent one Has deformation of the second measuring membrane in one of the signal processing unit supplied absolute pressure variable.

A further advantageous embodiment of the pressure sensor according to the invention can provide that the embodiment provide that the absolute pressure transducer and / or the relative pressure transducer is or are formed on semiconductor chips, in particular silicon chips.

A further advantageous embodiment of the pressure sensor according to the invention can provide that the embodiment provide that the absolute pressure transducer is formed on a separate semiconductor chip, in particular a silicon chip, to the relative pressure transducer. In particular, the embodiment can provide that the absolute pressure transducer is formed on a separate semiconductor chip, in particular a silicon chip, to the relative pressure transducer.

A further advantageous embodiment of the pressure sensor according to the invention can provide that the absolute pressure transducer is a capacitive absolute pressure transducer.

An alternative embodiment of the pressure sensor according to the invention can provide that the absolute pressure transducer is based on a piezoelectric layer.

• 1: einen Schnitt durch ein Ausführungsbeispiel eines erfindungsgemäßen Drucksensors zum Bestimmen einer Differenzdruckgröße.

The invention is explained in more detail with reference to the following drawing. It shows:

• 1 : a section through an embodiment of a pressure sensor according to the invention for determining a differential pressure variable.

1 shows a section through an embodiment of a pressure sensor according to the invention 1 . This includes a diaphragm seal 30th with a diaphragm seal body made up of several parts 31a , 31b , 31c and a relative pressure transducer 20th as well as an absolute pressure transducer 70 .

The two pressure transducers are made from a semiconductor material, in particular silicon, and can in particular be configured separately from one another as each independent sensor element.

The diaphragm seal body 31a , 31b , 31c comprises a substantially massive block 31a made of a metal, in particular made of a steel or stainless steel, and a carrier body 31b as a carrier for the two pressure transducers 20th , 70 serves. The massive block 31a has a separating membrane on one side surface 37a on. The separating membrane 37 closes a pressure receiving chamber which is integrated into the solid block on the outside 38a from. In the actual measuring operation, it acts on that of the massive block 31a remote side of the separating membrane 37a a process pressure originating from a medium p1 .

The process pressure p1 is via a first pressure-communicating path 34a to the relative pressure transducer 20th guided. To this end, the first pressure-communicating path is 34a filled with a pressure transmission fluid, so that this is also referred to below as hydraulic paths. The first hydraulic path 34a extends from a first opening 35a the pressure receiving chamber 38a through the massive block 31a via a capillary tube system 31c to a second opening 36a . Via the second opening 36a the first hydraulic path opens 34a in one in the support body 31b integrated pressure chamber 32 that is the process pressure p1 a front 21a a first measuring membrane 21 of the relative pressure transducer 20th feeds. Both the pressure chamber 32 as well as the first hydraulic path 34a are for transmitting the corresponding pressure with a transmission fluid 39 filled.

To the volume of the transmission fluid 39 in the pressure chamber 32 to keep it as low as possible, the pressure sensor 1 also one in the pressure chamber 32 introduced packing 33 on. Through the packing 33 there are cavities between the walls of the pressure chamber and the pressure transducers 20th , 70 each in a recess of the packing 33 can be filled in.

A second pressure communicating path 34b extends from a further second opening 36b in the support body 31 b via a capillary tube system 31c through the massive block to another first opening 35b . The other second opening 36b is such in the support body 31b provided that one via the second pressure-communicating path 34b transmitted second pressure p2 a back 21b the first measuring membrane 21 of the differential pressure transducer 20th is fed. The capillary tube system 31c is designed such that it is connected to the further first opening 35b in the vicinity of a measuring point in which the diaphragm seal for controlling / monitoring a process is installed, so that the pressure sensor is an ambient pressure as the second pressure p2 is fed.

Through the one at the front 21a the first measuring membrane 21 applied process pressure p1 and the one at the back 21b the first measuring membrane 21 applied ambient pressure p2 experiences the first measuring membrane 21 a pressure-dependent deflection. The pressure-dependent deflection can in turn, for example, through in the first measuring membrane 21 integrated piezoresistive elements are recorded by measuring technology, so that a relative pressure variable is determined by a first circuit 22nd can be determined for converting the pressure-dependent deflection. Alternatively, instead of the piezoresistive elements, capacitive elements can also be used to measure the pressure-dependent deflection.

About the pressure chamber 32 is also the process pressure p1 also on a front 71a a second measuring membrane 71 of the absolute pressure transducer. A pressure chamber (vacuum chamber) adjoins a rear side of the second measuring membrane, which is closed by the second measuring chamber so that the second measuring membrane is exposed to the process pressure p1 dependent deflection, which in turn is measured by a second circuit 72 can be recorded in order to determine an absolute pressure measured variable. The absolute pressure transducer thus only measures the process pressure (regardless of the ambient pressure).

The pressure sensor 1 further comprises a signal processing unit 80 to which the pressure variable (process pressure and ambient pressure) recorded by the respective pressure transducer is supplied. The signal processing unit 80 can for example comprise a microprocessor. The pressure sizes can be via electrical lines 81 from the first and second electrical circuits to the signal processing unit 80 be led.

The signal processing unit 80 is set up for a change in the ambient pressure p2 to be determined on the basis of the absolute pressure size and the relative pressure size.

wobei Prel die Relativdruckgröße des Relativdruckmesswandlers, Pabs die Absolutdruckgröße des Absolutdruckmesswandlers und α ein Anpassungs- oder Kalibrierungskoeffizient darstellen.For example, the signal processing unit can be set up to continuously check whether the following equation is met: $$\text{Prel}=\mathrm{\alpha }\text{Pabs}$$

where Prel is the relative pressure variable of the relative pressure transducer, Pabs the absolute pressure variable of the absolute pressure transducer and α represents an adaptation or calibration coefficient.

wobei Prd ein der Signalverarbeitungseinheit zugänglich gemachter, bspw. abgespeicherter, ortsüblicher Raumdruck ist und L[%] eine Änderung des ortsüblichen Luftdrucks über die Jahreszeiten, Wetterstand, Temperatur usw.. in Prozent, wobei im Normalbetrieb vorzugsweise gilt, dass P2 = Prd.The signal processing unit 80 can also be set up to detect a change in the ambient pressure if: $$\left|\frac{\text{P.}2-\text{Prd}}{\text{Prd}}\right|>n\cdot \mathrm{L.}\left[\%\right],n\in N$$

where Prd is a, for example, stored, customary room pressure made accessible to the signal processing unit and L [%] is a change in the customary local air pressure over the seasons, weather conditions, temperature, etc. in percent, whereby in normal operation it preferably applies that P2 = Prd.

List of reference symbols

1

Pressure sensor

20th

Relative pressure transducer

21

First measuring membrane

21a

First side of the first measuring membrane

21b

Second side of the first measuring membrane

22nd

First circuit for converting the pressure-dependent deformation of the first measuring membrane into a differential or relative pressure variable

30th

Diaphragm seal

31a

Massive block of the diaphragm seal body

31b

Carrier body

31c

Capillary tube system

32

Pressure chamber

33

Packing

34a

First pressure-communicating or hydraulic path

34b

Second pressure communicating path

35a, 35b

First opening

36a, 36b

Second opening

37a

Separating membrane

38a

Pressure receiving chamber

39

Pressure transmission fluid

70

Absolute pressure transducer

71

Second measuring membrane

71a

First side of the second measuring membrane

71b

Second side of the second measuring membrane

72

Second circuit for converting the pressure-dependent deformation of the measuring membrane into an absolute pressure variable

80

Signal processing unit

81

Electric lines

p1

Process pressure

p2

Ambient pressure

Claims (7)

Pressure sensor (1) for determining a relative pressure variable, comprising: - A relative pressure transducer (20) with a first measuring membrane (21) and a first circuit (22) for converting a pressure-dependent deformation of the first measuring membrane (21) into the relative pressure variable, - an absolute pressure transducer (70) for determining an absolute pressure variable, - A diaphragm seal (30) with a diaphragm seal body (31 a, 31 b, 31 c) in which there is a pressure chamber (32) filled with a transmission fluid (39), in which a filling body (33) is arranged with two recesses to create cavities between Walls of the pressure chamber (32) and the relative pressure transducer (20) and absolute pressure transducer (70) arranged in the recesses to be filled, a first pressure-communicating path (34a) between a first opening (35a) and a second opening (36a) through the pressure transmitter body ( 31), the first opening (35a) being closed by a separating membrane (37a) to which a first pressure (p1) of a medium can be applied in order to introduce the first pressure (p1) into the first path (34a), wherein the first path (34a) is filled with the transmission fluid (39) and opens at one of the second openings (36a) in the pressure chamber (32), so that the absolute pressure variable determined by the absolute pressure transducer (70) is the represents the first pressure (p1) and, furthermore, the relative pressure transducer is acted upon by the first pressure (p1) on a first measuring membrane side (21a) of the first measuring membrane (21), a second measuring membrane side (21b) of the first measuring membrane (21) communicating via a second pressure An ambient pressure (p2) is applied to the path (34b), so that the deformation of the first measuring membrane represents the relative pressure variable between the first pressure (p1) and the ambient pressure (p2); - A signal processing unit (80) which is set up to determine an undesired change in the ambient pressure on the basis of the absolute pressure variable and the relative pressure variable. Pressure sensor after Claim 1 , wherein the signal processing unit is also set up to determine a change in the ambient pressure (p2) if the following applies: $$\left|\frac{\text{P.}2-\text{Prd}}{\text{Prd}}\right|>n\cdot \mathrm{L.}\left[\%\right],n\in N$$

where Prd is a, for example, stored, customary room pressure made accessible to the signal processing unit and L [%] represents a change in the customary air pressure over the seasons, weather conditions and / or temperature. Pressure sensor according to one of the preceding claims, wherein the absolute pressure transducer has a second measuring membrane (71) to which the first pressure (p1) is also supplied on a first membrane side and to which a vacuum is applied on a second membrane side, the absolute pressure transducer also having a second circuit ( 72) for converting a pressure-dependent deformation of the second measuring membrane (71) into an absolute pressure variable fed to the signal processing unit (80). Pressure sensor according to one of the preceding claims, wherein the absolute pressure transducer and / or the relative pressure transducer is or are formed on semiconductor chips, in particular silicon chips. Pressure sensor according to the preceding claim, wherein the absolute pressure transducer is formed on a separate semiconductor chip, in particular a silicon chip, to the relative pressure transducer. Pressure sensor according to one of the preceding claims, wherein the absolute pressure transducer is a capacitive absolute pressure transducer. Pressure sensor according to one of the Claims 1 to 6th , whereby the absolute pressure transducer is based on a piezoelectric layer.

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